For the second time in four years, officials at the Matthaei Botanical Gardens are paving its driveways to stave off concerns about the protection of nearby wetlands.

The episode highlights the difficulties that even the most ecologically conscious organizations face in balancing environmental stewardship with the financial bottom line.

In 2005 officials had the asphalt driveways replaced with gravel in hopes that it would filter oil and water runoff from the parking lot and prevent it from ending up in nearby wetlands.

The runoff often ends up in Fleming Creek, a water source to Ann Arbor facilities like Radrick Farms Golf Course and Radrick Recreation Area.

But the gravel proved to cause more problems than it solved. As the gravel was packed down, it didn’t absorb runoff, which just ended up back in the wetlands, as had been the case with the asphalt.

Officials are hopeful that by repaving the driveways now — this time reverting back to asphalt — they will be able to better control water quality.

Botanical Gardens Director Robert Grese wrote in an email to the Daily that the cost of the repaving is $360,000.

In an e-mail response to a complaint from an Ann Arbor resident about the current project, Grese laid out the problems with the gravel option.

“The gravel was not as porous as we had hoped,” Grese wrote in the e-mail that was passed along to the Daily. “Once it was packed down, something like 80-90 percent of the water ran off rather than soaking through much of the surfaces.”

In addition to the gravel’s inability to absorb the runoff, April Pickrel, visitor services coordinator, said the maintenance of the gravel also caused problems for the wetlands.

“We had to spray the gravel with a petroleum-based product,” she said. “Both the product and dust were filtering into the constructed wetlands.”

In response to the complaint, Grese also wrote that the gravel needed constant maintenance and was often riddled with potholes. He added that it was also difficult to remove snow in the winter.

Though Pickrel said that one of the reasons officials installed the gravel was because it was better suited for natural areas like the botanical gardens, the problems with the gravel seemed to outweigh the benefits.

She added that regular asphalt isn’t an ideal material for the project, but it’s the best they could afford.

“We would ideally have permeable asphalt,” Pickrel said. “(But) we lacked the funds to properly redo the surface.”

In addition to repaving the driveways, officials are building more rain gardens and managing vegetation to encourage prairie species. Both efforts will help filter the runoff before it reaches the wetlands, Grese wrote in the e-mail.

“Even though the paving itself isn’t permeable, we try to handle some of the water before it runs into the stream,” Grese wrote.

In addition to these projects, the staff is currently overseeing the construction of a children’s garden. They are also planning a labyrinth that is expected to begin development in the next two months.

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